MILK-PLAXT OPERATION 
21 
of bottles washed per man-hour was 1,044, 342, and 199 for the three 
methods, respectively. These numbers were not greatly different 
from those given in Table 7, upon which the costs in Figure 15 were 
based. The cost of labor at the plants where the data were obtained 
was approximately 20 cents an hour in 1914. At that time the aver- 
age purchase price of the machines used in the plants was approxi- 
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Fig. 15. 
methods 
Comparative costs for labor and for interest and depreciation on equipment, with three 
thods of washing bottles, based on labor requirements at 113 plants. (Prices of 1921.) 
mately $1,500 for the automatic machines and $175 for the brush wash- 
ers. The lines representing the automatic and the brush-washing types 
intersect at about 2,300 bottles, indicating that when this number of 
bottles was reached it would have paid a dealer to consider the economy 
of changing from an ordinary brush washer to the automatic machine. 
By comparing Figures 15 and 16 it is apparent that even though 
equipment is much more expensive now (1922) than in 1914, the 
